Examination of Fe-Sn Intermetallic Layer Formation on C45 Steel in Calm SAC305 Solder Melt

Selective soldering tools, such as nozzles and soldering irons are made of iron, or high purity ARMCO iron. The lifetime of these components is limited to around one month of continuous operation due to a degradation process during which the reactive solder melt dissolves iron atoms from the tool. A physical simulator was designed and produced to study the reaction between C45 steel samples and calm SAC305 solder melt. Experiments were performed up to 20 days of reaction which was followed by scanning electron microscope based microstructure analysis. It was shown that after a few days of reaction, the SAC305 alloy dissolved a notable amount of Fe. Increasing the reaction time a clearly distinguishable Fe-Sn intermetallic layer formed at the C45 steel/solder melt interface. The thickness of the intermetallic layer increased with further increasing the reaction time.